Yvonne Rainer is a lady who likes to move her body in different ways. She likes to dance and make cool movements with her arms and legs. She's been dancing and choreographing for a long time, and people really like to watch her dance because it's different and creative.
Yvonne Rainer is important because she changed the way people think about dance. In the olden days, people thought that dance had to be pretty and perfect with everyone moving in the same way. But Yvonne Rainer didn't like that. She thought that dance could be different and express more emotion and ideas. So she created a new style of dance called "postmodern dance" that was more about expressing emotions and feelings through movement.
She also made a lot of movies called "experimental films" where she took different images and sounds and mixed them together. Some people really like her movies, while others don't understand them. But that's okay because art is supposed to make you feel something different.
So basically, Yvonne Rainer is a lady who loves to dance in new and creative ways, and she's important because she changed the way people thought about dance and art.